During combustion in an internal combustion engine, an air/fuel mixture is delivered through an intake valve to cylinders and is compressed and combusted therein. After combustion, the pistons force the exhaust gas in the cylinders into an exhaust system. To efficiently control an internal combustion engine, a number of sensors typically provide feedback for controlling engine system actuators. An engine control module receives inputs, such as an engine speed, flow rates, pressures and temperatures, from a number of sensors and controls the amount of fuel provided to the engine as well as air intake and exhaust system actuators in response to the inputs. Accurate inputs improve the ability of the engine control module to reduce emissions and improve fuel economy of the engine.
Complexity of engine control systems typically increases as engine system designers seek to improve durability, power, fuel economy, and reduce combustion noise while complying with government-mandated emissions standards. As additional sensors are included in an engine system, the system cost and weight increase. Accordingly, it is desirable to eliminate and synthesize one or more sensors based on available inputs and system parameters such that control algorithms can operate using synthesized sensor input while eliminating the system cost, weight, and servicing requirements associated with one or more physical sensors.